Packet communication networks consist of a plurality of communication nodes connected together by communication links. These communication nodes may be terminal equipment, such as computer stations, mobile communication terminals or application servers. These communication nodes may also be intermediate equipment, such as switches or routers, which serve to provide interconnection of the terminal equipment and serve to provide routing of data between the terminal equipment.
The communication links are based on highly diverse physical transmission technologies, whether they be wired (optical fibre, Ethernet, etc.) or wireless (WiFi, WiMax, satellite connection, etc.). These transmission technologies intrinsically lead to different transmission channel properties, in particular in terms of variability of available bandwidth.
These packet communication networks serve to implement a great diversity of services, such as for example services of the VoIP (Voice over IP) type, audiovisual transmission services or Web services. These services have requirements in terms of bandwidth and/or latency that depend on the service in question. To allow the development of services having constraint requirements in terms of bandwidth and/or latency of packet communication networks, QoS (Quality of Service) management technologies are implemented. These technologies are based on the definition of a set of classes of service (CoS) each corresponding to transmission constraints specifically established to support a given service. It is for example the case of the DiffServ (Differentiated Services) technology, as defined in particular in the standard documents RFC 2474 and 2475. Priorities are respectively allocated to the various classes of service and the intermediate items of equipment of a communication network that deal with congestion base themselves on these priorities in order to eliminate packets among those with the lowest priority and thus assist the transmission of packets among those having the highest priority. It is then the that the packets are colored, meaning that they are respectively marked by classes of service CoS and the network equipment that has to process the packets shall apply to the packets a QoS plan dependent on the classes of service CoS.
The most tricky communication links to be managed in terms of quality of service are the links based on wireless communication technologies since such links are subject to high variations of bandwidth according to changes in environment (signal attenuation, noise, interference, etc.). This is in particular the case with satellite links, the performances of which depend on climatic conditions (rain, fog, etc.).
It is therefore desirable, under these circumstances, to detect congestion situations, which may occur, on the same transmission link, vis-à-vis one or more classes of service and not occur vis-à-vis one or more other classes.
It is also desirable to provide a solution that is independent of a transport protocol (transport layer of the OSI (Open Systems Interconnection)) model used for transporting the data on the transmission link.
It is also desirable to provide a solution that complies with the network architecture recommendations of the OSI model.
It is also desirable to provide a solution that is simple to implement and in particular does not require any temporal synchronisation of the items of network equipment in the communication network.